The HLA-D region, or class II genes, in the human major histocompatibility complex consists of three multigene subregions (i.e., DR, DQ, DP) that encode a highly polymorphic series of cell-surface glycoproteins involved in regulating the immune response. HLA-D region antigens vary among different ethnic groups. those antigens that are normally associated with a particular DR specificity in a caucasian population may be absent in a non-caucasian population and a different specificity substituted. These correlations are important because of the relationship found between particular alleles at the HLA-D region and a variety of human diseases. A major objective of this proposal is the definition and characterization of HLA-D region antigens in the African American population. A better definition of HLA polymorphism in different ethnic groups has important biomedical implications in areas such as histocompatibility matching for organ transplantation and the greater participation of ethnic minorities in national bone marrow transplantation programs. The focus of this proposal is the genomic analysis of a HLA-"DR2 like" cell by DNA restriction enzyme analysis, locus and allele specific oligonucleotide probes, and sequence analysis. The study will use the above techniques to address the following specific aims: to test whether there are differences in hybridization patterns between DNA from HLA-DR2 subtypes and the DR2-like cell; to compare RFLP profiles of KWH with published DR subtypes; to contrast allelic hypervariable sequences in domain I of in vitro amplified DNA from KWH (DR2-like cell) and other DR2 subtypes and to sequence KWH.